Colorimetric method for determining the color of wine

ABSTRACT

The invention relates to a method for determining the color of wine from grapes. The method involves digesting the grapes in a pectolytic enzyme solution and a sulfur dioxide solution; diluting the solution with diluted acid and spectrophometric reading of the resulting solutions. The invention also relates to a program that calculates the probable color of the wine based on the spectroscopic data and physical-chemical parameters of the wine.

FIELD OF THE INVENTION

The present invention describes a process for the determination of the colour of wine from the grape. This process consists of digestion of the grapes with a solution of pectolytic enzymes and a solution of sulphurous anhydride, dilution of the solution with diluted acid and spectrophotometric reading of the resultant solution and a programme that calculates the wine's probable colour from spectroscopic data and physicochemical parameters of the wine.

BACKGROUND OF THE INVENTION

The wine's colour or intensity of colour is mainly caused by anthocyanins. There are trials and methods which take four hours that correlate the anthocyanin content in the grape with that of the wine. However, bulk wine on the market is paid by degree and point of colour and not by mg/l of anthocyanins; furthermore, there is not a high correlation (less than 0.5) between the colour degree and the anthocyanin content. Therefore, at present there is no suitable method for the determination of the intensity of the colour of wine from the grape.

OBJECT OF THE INVENTION

The present invention describes a method to predict the wine's probable colour, which will be obtained with the grapes analysed in a rapid and highly accurate way, by means of the extraction of colouring matter, spectrophotometric reading and exportation of the spectrophotometric data using a computer programme which, in turn, calculates the wine's probable colour from the spectrophotometric data and physicochemical parameters of the wine.

DETAILED DESCRIPTION OF THE INVENTION

The process to experimentally obtain the wine's probable colour consists of two parts:

-   a) Extraction of the colouring matter from the grapes and     spectrophotometric measurement. -   b) Calculation of the wine's colour from the spectrophotometric data     and physicochemical parameters of the wine by means of a computer     programme.

The seeded grapes can be digested at a temperature below 80° C. in the presence of a solution of pectolytic enzymes and an acid solution of sulphurous anhydride. Once extraction has finished, the mixture is purified, for which various different techniques such as flocculation, filtration or centrifugation can be used. The limpid solution is diluted with a diluted acid, preferably using hydrochloric acid. The resultant solution is read on a spectrophotometer in an interval of wavelengths between 280-700 nm.

A computer programme calculates the wine's probable colour from the spectrophotometric data and different analytical parameters of the wine fed into the programme. The analytical parameters are:

-   Total acidity -   PH -   Probable degree -   Obtaining an accuracy of IC (real intensity of colour)=PC (Probable     colour according to the process)±1.48

EXAMPLE

The invention is described by means of an example which does not limit the scope of the invention.

Example 1

This illustrates the method of extraction and the results obtained for different samples.

A 1% solution of pectolytic enzymes is added to 100 grams of seeded grapes, which is then triturated and an acid solution of sulphurous anhydride is added. The mixture is stirred at 80° C. for 10 minutes. 2 ml of the sample are centrifuged at 8000 rpm. The sample is diluted by 1/10 with diluted hydrochloric acid and a UV spectrum—visible between 200 and 700 nm—is performed.

Following official methods, the pH, alcohol content and total acidity are determined on the grapes.

In a parallel way, micro-vinifications are carried out to calculate the real value of the wine's colour intensity. The results obtained are shown below, where:

-   -   N is the sample number     -   P°D is the probable degree     -   TA is the total acidity     -   D280e and D520e are the absorbancies at 280 and 520 nm of the         grape extract obtained for the probable colour determination.     -   ICv is the real intensity of colour of the wine obtained.     -   PC is the wine's intensity of colour, calculated according to         the method.

N P° D PH TA D280e D520e D280v ICv PC 1 14.8 3.8 3.8 136 77 70 9.2 8.96 2 14.2 3.7 4.4 137 82 62 11.4 9.82 3 14.6 3.5 5.5 160 90 67 13.36 12.1 4 13.5 3.7 4.8 155 90 65 13.44 10.82 5 14.7 3.7 5.3 144 76 65 10.49 9.62 6 14.8 3.7 4.4 150 86 62 12.5 10.8 7 13.2 3.6 4.4 176 92 69 13.24 11.51 8 14.8 3.7 4.2 182 86 42 9.52 11.1 9 12.8 3.5 6.2 127 52 57 5.46 6.54 10 14.2 3.4 5.2 163 87 60 10.79 12.3 11 12.5 3.4 5.3 75 21 57 1.95 2.31 12 13.8 3.7 4.4 177 98 67 11.79 12.14 13 14.8 3.8 4.7 171 95 46 11.84 11.84 14 14.8 3.5 4.9 170 90.8 42.5 9.04 12.08 15 14.8 3.7 5.0 176 86 54 13 11.12 16 14.8 3.7 3.7 158 85 47.84 9.30 10.37 17 14.8 3.6 5.0 182 101 50 12.06 13.25 18 13.9 3.5 4.9 150 82 53 9.35 10.7 19 14.2 3.4 6.2 168 90.2 60.7 13.24 12.58 20 13.8 4.1 4.1 163 94 51 9.77 9.94 21 14.8 3.4 5.5 146 66 50 10.95 9.19 22 14.8 3.6 5.2 172 77 54 10.82 10.12 23 14.1 3.6 5.1 182 92 50 10.27 11.93 24 14.0 3.5 5.2 159 68 33 8.14 9.02 25 14.8 3.6 5.2 153 79 62 12.1 10.27 26 14.3 3.6 5.6 174 87 53 12.67 11.61 27 11.8 3.3 6.1 136.6 59 33 8.66 7.61 28 14.7 3.8 4.5 168 96 46 12.97 12.10 29 13.6 3.9 4.2 182 107 46 13.47 12.10 30 14.8 3.6 4.1 176 86 65 8.23 11.21 31 14.8 3.7 4.6 160 79 26 7.80 10.06 32 13.1 3.3 6.2 149 63 57 7.69 8.63 33 13.6 3.5 5.0 159 72 54 10.1 9.24 34 14.2 3.9 4.5 156 68 41 8.51 7.76 35 14.8 3.7 4.5 187 98.8 42 13.96 12.76 36 14.8 3.8 5.0 123 63 44 5.83 7.40 37 14.8 3.6 4.2 188 100 51 13.46 13.24 38 14.8 3.8 4.4 180 98 51 10.34 12.11 39 14.8 3.8 4.5 166 74 59 7.50 8.86 40 14.8 3.7 5.9 141 68 34 9.14 8.53 41 14.8 3.8 4.3 148 81 36 8.52 9.75 42 14.8 3.7 5.5 151 77 39 10.35 9.63 43 14.2 3.7 4.6 151 67 43 10.78 8.41 44 14.8 3.6 3.9 191 105 38 15.25 13.58 45 14.8 3.6 5.5 144 78 64 7.56 10.13 46 14.5 3.6 3.5 206 98 37 10.64 13.09 47 13.5 3.6 5.5 146 71 58 9.32 9.02 48 12.9 3.7 5.1 141 80 49 9.29 9.39 49 14.8 3.8 4.7 195 105 53 11.48 13.05 50 13.1 3.7 4.4 155 80 49 9.67 9.39 51 12.4 3.7 3.8 165 87 43 9.37 9.96 52 14.0 3.6 5.1 211 93 50 12.5 12.53 53 13.6 3.7 4.6 160 88 29 8.68 10.68 54 14.8 3.9 4.1 194 97 49 11.00 12.01 55 14.8 3.7 4.4 161 83 58 10.0 10.41 56 14.6 3.9 4.0 162 100 60 12.06 11.50 57 14.7 3.6 4.9 212 111 65 12.24 15.23 58 13.8 3.9 6.0 155 84 47 7.79 9.92 59 14.2 3.7 4.6 164 81 47 9.91 10.17 60 13.9 3.5 6.0 133 59 45 3.70 7.60 61 13.2 3.7 4.6 148 61 69 5.93 7.28 62 14.8 3.7 4.6 170 74 31 8.82 9.46 63 14.8 3.7 4.6 161 64 23 10.00 8.09 64 14.8 3.7 4.6 182 88 70.2 12.17 11.35 65 14.8 3.8 4.2 182 79 62 10.31 10.03 66 12.6 4.0 4.1 160 84 67 9.66 8.91 67 13.7 3.6 4.6 171 74 65 10.76 9.50 68 14.5 3.7 5.1 153 63 65 9.22 7.97 69 14.5 3.6 5.0 160 75 62 10.83 9.69 

1. A colorimetric process for determination of the colour of wine from a grape, comprising: a) extraction from the grape a portion of colouring matter of the grape in a solution of pectolytic enzymes at a temperature below 80° C. in the presence of an acid solution of sulphurous anhydride; b) purification of the extraction mixture; c) dilution of the solution with a diluted acid; d) reading of the resultant solution by using a spectrophotometer in an interval of wavelengths between 280-700 nm, e) obtaining pH, total acidity, and probable degree of the grape, and f) calculation of the wine's probable colour from spectroscopic data, pH, total acidity, and probable degree, by means of a computer program, g) reporting of the probable colour in a user readable format.
 2. A colorimetric method for determining the probable colour of wine from a grape, the process comprising: extracting at least a portion of colouring matter of the grape in an acidic solution of pectolytic enzymes and sulphurous anhydride at a temperature below 80°C. to yield an extraction mixture; purifying the extraction mixture; diluting the purified extraction mixture with a diluted acid; measuring spectroscopic properties of the diluted extraction mixture by using a spectrophotometer in an interval of wavelengths between 280-700 nm, and obtaining pH, total acidity, and probable degree of the grape; calculating the wine's probable colour from the spectroscopic data, pH, total acidity, and probable degree by means of a computer program; and reporting the probable colour calculated by the computer program.
 3. The method of claim 2, wherein the dilute acid is hydrochloric acid.
 4. The method of claim 2, wherein the step of measuring spectroscopic properties of the diluted extraction mixture includes measuring the absorbance of the diluted extraction mixture at about 280 nm and about 520 nm. 